1.4 Bonding

Question 1

What is an ionic bond?

Answer 1

A bond between a positive and negative ion. The ions are held together by strong electrostatic attraction.

Question 2

Draw a dot-and-cross diagram for the ionic compound NaCl

Answer 2

Question 3

What is an ionic crystal?

Answer 3

A giant lattice of ions, held together by the electrostatic attraction of oppositely charged ions.

Question 4

Why do ionic compounds have high melting points?

Answer 4

Ionic compounds have strong electrostatic attraction between the oppositely charged ions which requires a lot of energy to break and is required to melt the compound. Therefore, ionic compounds have high melting points.

Question 5

What is a covalent bond?

Answer 5

A bond formed that involves the sharing of electron pairs between atoms.
It forms due to the electrostatic attraction between the positive nuclei of the bonded atoms and the negative electrons which are between the two nuclei.

Question 6

What is a dative (co-ordinate) covalent bond?

Answer 6

A type of covalent bond whereby both electrons in the shared pair are donated by one of the bonding atoms only.

Question 7

Define electronegativity

Answer 7

The power of an atom to attract the electron density in a covalent bond towards itself.

Question 8

Define bond polarity

Answer 8

Bond polarity refers to the separation of electric charge along a bond. Polar bonds arise when the electrons in the bond are not shared equally.

Question 9

Explain what is meant by a temporary dipole

Answer 9

Electrons are constantly moving around the nucleus. At any one time there will be an uneven distribution of electrons, making one half of the molecule more negatively charged than the other. This creates a temporary dipole.

Question 10

Explain what is meant by a permanent dipole

Answer 10

If two atoms that are covalently bonded have different electronegativities, a polar bond forms. The more electronegative atom draws more of the negative charge towards itself and away from other atom, producing a ∂- region and a ∂+ region. This is a permanent dipole.

Question 11

Explain what is meant by an induced dipole

Answer 11

An induced dipole is created when electron distribution around a molecule is influenced by a charged particle.

Question 12

Compare the bond character in a covalent bond, intermediate bond and ionic bond

Answer 12

Covalent bond - electrons shared equally between atoms, leading to no overall charge.

Intermediate bond - electrons shared unequally so there are partial charges on the atoms.

Ionic bond - complete transfer of electrons between atoms to produce ions with full charges.

Question 13

What types of intermolecular forces are there?

Answer 13

• Temporary dipole interactions
• Permanent dipole interactions
• Hydrogen bonding

Question 14

How do temporary dipole interactions occur between molecules?

Answer 14

There is an uneven distribution of electrons around the molecule. This creates an uneven distribution of charge, which creates a temporary dipole in the molecule. The temporary dipoles induce dipoles in neighbouring molecules.

Question 15

What is a permanent dipole-dipole interaction?

Answer 15

The electrostatic attraction between oppositely charged permanent dipoles of neighbouring molecules.

Question 16

What are hydrogen bonds?

Answer 16

Question 17

Why does water have a high melting and boiling point?

Answer 17

Hydrogen bonds form between water molecules due to the electronegative oxygen and the slightly positive hydrogen atom. Hydrogen bonds require a lot of energy to break.

Question 18

Why are alcohols soluble in water?

Answer 18

Alcohols form hydrogen bonds with the water molecules due to the electronegative oxygen being bonded to a hydrogen in the -OH group. This makes them soluble in water.

Question 19

How can the electron pair repulsion theory be used to predict the shapes of simple molecules and ions?

Answer 19

The shape of a molecule is determined by the arrangement of electron pairs around the central atom. The electron pairs repel which lead to specific shapes depending on how many electron pairs are present. There is greater repulsion between lone pairs compared with bonding pairs.

Relative repulsion:

Lone pair-lone pair> lone pair-bonding pair> bonding pair-bonding pair

Question 20

Name the shape of BeCl2. What is the bond angle?

Answer 20

Question 21

Name the shape of BCl3. What is the bond angle?

Answer 21

Question 22

Name the shape of CH4. What is the bond angle?

Answer 22

Question 23

Name the shape of NH3. What is the bond angle?

Answer 23

Question 24

Name the shape of NH +. 4
What is the bond angle?

Answer 24

Question 25

Name the shape of H2O. What is the bond angle?

Answer 25

Question 26

Name the shape of SF6. What is the bond angle?

Answer 26